178 DOVE ON THE ELECTRICITY OF INDUCTION. 



of unmagnetic metals into the extra spiral appeared to cause no 

 diminution of the spark, even when this was composed of five 

 connected spirals. 



82. These facts tend therefore also to explain why a spring 

 which breaks connexion in azimuth 135° on the insertion of 

 iron into the spiral, produces a diminution, although but slight, 

 in the vividness of the spark, and why the physiological action 

 also, with the connexion I and II through the body, appears 

 somewhat diminished, although, without the insertion of the 

 spiral in this position of the keeper, the primary current would 

 have already exceeded its maximum. As a general conclusion, 

 therefore, in whatever part of the second quadrant the interrup- 

 tion is effected, the first extra current will always have been in- 

 creased for a longer time by the inserted iron than the second ; 

 the primaiy current will therefore have lost more in the first 

 quadrant by means of the extra current than it will gain up to 

 the point of interruption in the second by the insertion of iron. 

 It also appears that the intensity of the primary current in the 

 second quadrant decreases much more slowly than it increases 

 in the first quadrant ; for the sparks and shocks are much more 

 intense when the spring breaks connexion in azimuth 135° than 

 when that is effected in azimuth 45°. The reason why this 

 occurs when no spiral is inserted is, because the coils of the 

 keeper itself, with the nucleus of iron which they enclose, may 

 in a certain sense be considered as its own extra spiral. 



83. If spark experiments are to be instituted, correspond- 

 ing to the physiological experiments in which the body closed 

 the circuit either by I and III or II and III, then an arrange- 

 ment must be made to break the metallic connexions I and 

 III and II and III at the instant the spring breaks connexion 

 at u. This was effected by the addition of a fourth cylinder 

 10^ (fig. 7)j identical with the cylinder iv^, on which u presses, 

 and moreover insulated from the axis, upon which any two of 

 the connexions I and III or II and III slide with a certain 

 pressure, the one continuously, which is clamped at 14) in the 

 stand G, the other intermittent, proceeding from 13) in the 

 stand F. If the clamp 7) is connected with 12) by a wire in- 

 dicated by the dotted line in fig. 7? and in the same manner 

 15) is connected with 4) by a second vpire, then, at the instant 

 the spring proceeding from 13) comes in contact with the wood, 

 the previously existing secondary connexion II and III is 



